DOCSLIB.ORG

A Unified Approach for the Enantioselective Synthesis of the Brominated Chamigrene Sesquiterpenes

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
A Unified Approach for the Enantioselective Synthesis of the Brominated Chamigrene Sesquiterpenes Author Manuscript Title: A Unified Approach for the Enantioselective Synthesis of the Brominated Cha- migrene Sesquiterpenes Authors: Alexander J. Burckle; Vasil H. Vasilev; Noah Burns This is the author manuscript accepted for publication and has undergone full peer review but has not been through the copyediting, typesetting, pagination and proofrea- ding process, which may lead to differences between this version and the Version of Record. To be cited as: 10.1002/anie.201605722 Link to VoR: http://dx.doi.org/10.1002/anie.201605722 COMMUNICATION A Unified Approach for the Enantioselective Synthesis of the Brominated Chamigrene Sesquiterpenes Alexander J. Burckle, Vasil H. Vasilev, and Noah Z. Burns* Abstract: The brominated chamigrene sesquiterpenes constitute a representative of the simplest members of the brominated large subclass of bromocyclohexane containing natural products, yet chamigrenes, specifically its isomeric natural product no general enantioselective strategy for the synthesis of these small counterparts, bromochamigrene[3,10,11] (3 and 4, molecules exists. Herein we report a general strategy for accessing Figure 1b). We thus devised a strategy that was capable of this family of secondary metabolites including the enantioselective providing facile access to numerous brominated spirodienes in synthesis of ()-- and ()-ent--bromochamigrene, ()-dactylone, enantioenriched form. and ()-aplydactone. Access to these molecules is enabled by a stereospecific bromopolyene cyclization initiated by the solvolysis of an enantioenriched vicinal bromochloride. Of the roughly 300 natural products that have been isolated and structurally characterized containing a bromocyclohexane motif (1, Figure 1a),[1a-c] more than 50 are represented by the brominated chamigrene sesquiterpenes (2, Figure 1a). Most members of this family differ in their level of saturation, halogenation, and oxygenation (3–8, Figure 1b). The structural variety within the halogenated chamigrenes is complemented by diverse biological activities, with noteworthy examples including antibacterial,[2] antifungal,[3] antiviral,[4] anthelmintic,[5] and anticancer[6] effects. To date, the total synthesis of (+)-elatol 6 by Stoltz and Grubbs[7a] constitutes the only enantioselective synthesis of a member of the halogenated chamigrene sesquiterpenes. A general enantioselective approach for the synthesis of this class of molecules has yet to be reported.[7b–e] Along these lines, we set out to develop a strategy that would enable rapid construction of the spirocyclic core and thus facilitate elaboration to structurally disparate members of this family of small molecules for further chemical and biological investigations. We were particularly intrigued by the cancer preventive agent dactylone (7)[8] and a related congener, aplydactone (8).[9] Dactylone has been shown to suppress phenotype expression at non-cytotoxic doses in human lung, colon, and skin tumor cell Figure 1. The halogenated chamigrene sesquiterpenes. a) Ubiquitous lines and therefore holds promise as a molecular tool for bromocyclohexane motif and bromochamigrene skeleton; b) representative anticancer studies.[8c] Dactylone and aplydactone were originally members of the natural product class; c) this approach. isolated from the sea hare Aplysia dactylomela in 1987, however the structure of aplydactone was not disclosed until 2001 with the assistance of X-ray crystallography.[9] In that report, it was We targeted isoprenoid-derived bromocycle 10 that could suggested that 8 may arise from an intramolecular [2 + 2] be rapidly elaborated to the spirocyclic chamigrene core (10 to 9, cycloaddition of 7. Accordingly, we selected dactylone 7 as a Figure 1c), providing a general way of accessing this class of synthetic target with the objective of also interrogating its natural products. While a bromonium-induced carbocationic conversion to aplydactone 8. We hoped this investigation would cyclization would provide a direct means to access candidate shed light on the feasibility of this transformation both in a carbocycles, no enantioselective bromopolyene cyclization biosynthetic and laboratory setting. We were confident that 7 protocols have been reported on natural product-relevant scaffolds.[12] Cognizant of this methodological gap, we saw an could be obtained directly from its corresponding deoxygenated precursor 9. This diene, while not yet having been isolated, is opportunity to use enantioenriched vicinal dihalides as progenitors of bromonium ions. Enantiopure bromonium ions have been previously generated from enantioenriched [*] A. J. Burckle, V. H. Vasilev, Prof. Dr. N. Z. Burns bromohydrin derivatives and have been captured in an intra- and Department of Chemistry, Stanford University intermolecular fashion.[12c,d,13b] However, to our knowledge the 333 Campus Dr., Stanford, CA 94305 (USA) generation and subsequent trapping of an enantioenriched E-mail: [email protected] bromonium ion from a vicinal dihalide has not been reported. Supporting information for this article is given via a link at the end of Recently our laboratory disclosed an enantioselective Schiff the document. This article is protected by copyright. All rights reserved COMMUNICATION base catalyzed di- and interhalogenation reaction of allylic With the requisite precursor in hand, we subjected 16 to alcohols, providing access to highly enantioenriched ionizing conditions in basic hexafluoroisopropanol (HFIP)[13] bromochlorides,[14a] dibromides, and dichlorides.[14b-d] We optimistic that an enantiopure non-racemizing bromonium ion hypothesized that subjecting these species to ionizing conditions could be generated and captured by the pendant allylic acetate. could facilitate the generation of an enantioenriched halonium To our delight, the cyclization proceeded smoothly and afforded ion that could be captured intramolecularly for productive bromocarbocycle 17 in 54% yield as a single isolated cyclization (12 to 10 via 11, Figure 1c). diastereomer with near-perfect enantiospecificity (90% ee 17; This plan called for the enantioselective dihalogenation of 96% enantiospecificity). Analogous dibromoalcohols were allylic alcohol 13 (Scheme 1), which can be prepared in one step observed to racemize under the ionizing conditions and were from commercially available geranyl acetate.[15] Using conditions unstable to the deoxygenation conditions. To our knowledge this previously disclosed by our laboratory, (R,S)-Schiff base 14- is the first example of the solvolysis and intramolecular capture catalyzed bromochlorination proceeded in good yield (66%) and of an enantioenriched dihalide. with excellent enantioselectivity (94% ee) on 4.4 g scale to We next sought to elaborate enantioenriched carbocycle deliver bromochloride 15. Two-step deoxygenation[14d] followed 17 to the spirocyclic framework relevant to the brominated by reacylation provided >1 g of bromochloro-geranyl acetate 16. chamigrene sesquiterpenes (Scheme 2). We envisioned that an isoprene Diels–Alder transformation with a corresponding exocyclic enone could provide the desired scaffold. Bromocycle 17 was cleanly dehydrated to the exocyclic olefin[16] with subsequent oxidative cleavage[17] affording ketone acetate 18 in good yield (62% over two steps). Facile elimination of the acetate to the exocyclic enone 19 occurred in the presence of DBU with mild heating, but attempts at its isolation led to rapid formation of unusual hetero- 20 upon concentration and standing. Circumventing isolation of this unstable intermediate, enone 19 was generated in situ and treated with dimethylaluminum chloride and excess isoprene,[18] and the desired Diels–Alder adduct was easily obtained as a 4.3:1 (52% 21 + 12% 22) mixture of separable epimers. Access to these diastereomeric spiroketones served as a convenient diversification point in our synthesis providing access to the doubly unsaturated, isomeric - and ent--bromochamigrenes (4 and 3, respectively). Scheme 1. Enantioselective dihalogenation and key solvolytic bromopolyene Transformation of spiroketones 21 and 22 to their cyclization. Reagents and conditions: a) NBS (1.05 equiv), ClTi(Oi-Pr)3 (1.1 corresponding exocyclic olefins was next required for the equiv), 20 mol % (R,S)-14, hexanes, –20 ˚C, 66%; b) triflic anhydride (1.2 synthesis of ent--bromochamigrene 4 and dactylone 7. An equiv), 2,6-lutidine (2.0 equiv), CH2Cl2, –78 ˚C, 85%; c) L-selectride (5.5 equiv), [19] THF, –78 ˚C to r.t., 58%; d) acetic anhydride (1.0 equiv), 4- initial survey of standard methylenation conditions failed to dimethylaminopyridine (0.05 equiv), triethylamine (1.2 equiv), CH2Cl2, r.t., convert any of the spiroketone (21) to the desired olefin 9. We 94%; e) potassium carbonate (1.5 equiv), hexafluoroisopropanol (0.05 M), r.t., reasoned that failed olefinations were due to the combination of 54%. the extremely hindered neopentyl ketone and the bulkiness of Scheme 2. Synthesis of (–)- -aplydactone, and (–)-- and (–)-ent--bromochamigrene. Reagents and conditions: a) thionyl chloride (1.5 equiv), triethylamine (5 equiv), CH2Cl2, –196 ˚C to –95 ˚C; b) ruthenium(III) chloride (0.02 equiv), sodium periodate (1.5 equiv), MeCN/CCl4/H2O, r.t., 62% from 17; c) 1,8- diazabicycloundec-7-ene (1.1 equiv), isoprene (20 equiv), Me2AlCl (3.5 equiv), PhMe, –78 ˚C to –10 ˚C 52% 21 + 12% 22; d) magnesium (8.0 equiv), titanium tetrachloride (2.0 equiv), THF/CH2Cl2, 0 ˚C to r.t., 43%; e) selenium dioxide (1.5 equiv), dioxane, 80 ˚C, 42%; f) 2-iodoxybenzoic acid (2.0 equiv), DMSO, r.t.,
Load more

Recommended publications
  • Biomolecules
    CHAPTER 3 Biomolecules 3.1 Carbohydrates In the previous chapter you have learnt about the cell and 3.2 Fatty Acids and its organelles. Each organelle has distinct structure and Lipids therefore performs different function. For example, cell membrane is made up of lipids and proteins. Cell wall is 3.3 Amino Acids made up of carbohydrates. Chromosomes are made up of 3.4 Protein Structure protein and nucleic acid, i.e., DNA and ribosomes are made 3.5 Nucleic Acids up of protein and nucleic acids, i.e., RNA. These ingredients of cellular organelles are also called macromolecules or biomolecules. There are four major types of biomolecules— carbohydrates, proteins, lipids and nucleic acids. Apart from being structural entities of the cell, these biomolecules play important functions in cellular processes. In this chapter you will study the structure and functions of these biomolecules. 3.1 CARBOHYDRATES Carbohydrates are one of the most abundant classes of biomolecules in nature and found widely distributed in all life forms. Chemically, they are aldehyde and ketone derivatives of the polyhydric alcohols. Major role of carbohydrates in living organisms is to function as a primary source of energy. These molecules also serve as energy stores, 2021-22 Chapter 3 Carbohydrade Final 30.018.2018.indd 50 11/14/2019 10:11:16 AM 51 BIOMOLECULES metabolic intermediates, and one of the major components of bacterial and plant cell wall. Also, these are part of DNA and RNA, which you will study later in this chapter. The cell walls of bacteria and plants are made up of polymers of carbohydrates.
    [Show full text]
  • Sugars As the Source of Energized Carbon for Abiogenesis
    Astrobiology Science Conference 2010 (2010) 5095.pdf SUGARS AS THE SOURCE OF ENERGIZED CARBON FOR ABIOGENESIS. A. L. Weber, SETI Institute, NASA Ames Research Center, Mail Stop 239-4, Moffett Field, CA, 94035-1000, [email protected] Abstract: As shown in Figure 1, abiogenesis has sev- eral requirements: (A) a source of organic substrates and chemical energy that drives the synthesis of (B) useful small molecules (ammonia, monomers, metabo- lites, energy molecules), and (C) a second synthetic processs that yields large replicating and catalytic polymers that control (D) the growth and maintenance of a primitive protocell. Furthermore, the required chemical energy must be sustained and effectively coupled to individual reactions to drive biosynthesis at a rate that counters chemical degradation. Energy coupling would have been especially difficult during the origin of life before the development of powerful enzyme catalysts with 3-D active sites. To solve this energy coupling problem we have investigated abio- genesis using sugar substrates whose energized carbon groups drive spontaneous synthetic self-transformation reactions that yield: biometabolites, catalytic mole- cules, energy-rich thioesters, amino acids, plausible alternative nucleobases and cell-like microstructures [1-8]. Recently, we demonstrated that sugars drive the synthesis of ammonia from nitrite [9]. The ability of sugars to drive ammonia synthesis provides a way to generate ammonia at microscopic sites of sugar-based origins processes, thereby eliminating the need for a planet-wide source of photochemically unstable am- monia. Figure 1. Major Synthetic Processes of Abiogenesis. [1] Weber A. L. (1998) Orig. Life Evol. Biosph., 28, 259-270. [2] Weber A.
    [Show full text]
  • An Overview of Biosynthesis Pathways – Inspiration for Pharmaceutical and Agrochemical Discovery
    An Overview of Biosynthesis Pathways – Inspiration for Pharmaceutical and Agrochemical Discovery Alan C. Spivey [email protected] 19th Oct 2019 Lessons in Synthesis - Azadirachtin • Azadirachtin is a potent insect anti-feedant from the Indian neem tree: – exact biogenesis unknown but certainly via steroid modification: O MeO C OAc O 2 H O OH O H O OH 12 O O C 11 O 14 OH oxidative 8 O H 7 cleavage highly hindered C-C bond HO OH AcO OH AcO OH for synthesis! H H of C ring H MeO2C O AcO H tirucallol azadirachtanin A azadirachtin (cf. lanosterol) (a limanoid = tetra-nor-triterpenoid) – Intense synhtetic efforts by the groups of Nicolaou, Watanabe, Ley and others since structural elucidation in 1987. –1st total synthesis achieved in 2007 by Ley following 22 yrs of effort – ~40 researchers and over 100 person-years of research! – 64-step synthesis – Veitch Angew. Chem. Int. Ed. 2007, 46, 7629 (DOI) & Veitch Angew. Chem. Int. Ed. 2007, 46, 7633 (DOI) – Review ‘The azadirachtin story’ see: Veitch Angew. Chem. Int. Ed. 2008, 47, 9402 (DOI) Format & Scope of Presentation • Metabolism & Biosynthesis – some definitions, 1° & 2° metabolites • Shikimate Metabolites – photosynthesis & glycolysis → shikimate formation → shikimate metabolites – Glyphosate – a non-selective herbicide • Alkaloids – acetylCoA & the citric acid cycle → -amino acids → alkaloids – Opioids – powerful pain killers • Fatty Acids and Polyketides –acetylCoA → malonylCoA → fatty acids, prostaglandins, polyketides, macrolide antibiotics – NSAIDs – anti-inflammatory’s • Isoprenoids/terpenes
    [Show full text]
  • Matrix-Assisted Laser Desorption/Ionization Time-Of-Flight
    Received: 26 November 2018 Revised: 29 January 2019 Accepted: 31 January 2019 DOI: 10.1002/rcm.8406 RESEARCH ARTICLE Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry analysis for characterization of lignin oligomers using cationization techniques and 2,5‐dihydroxyacetophenone (DHAP) matrix Amber S. Bowman | Shardrack O. Asare | Bert C. Lynn Department of Chemistry, University of Rationale: Effective analytical techniques are needed to characterize lignin Kentucky, Lexington, KY 40506, USA products for the generation of renewable carbon sources. Application of matrix‐ Correspondence assisted laser desorption/ionization (MALDI) in lignin analysis is limited because of Bert C. Lynn, Department of Chemistry, UK Mass Spectrometry Facility, University of poor ionization efficiency. In this study, we explored the potential of cationization Kentucky, A053 ASTeCC Building, Lexington, along with a 2,5‐dihydroxyacetophenone (DHAP) matrix to characterize model KY 40506‐0286, USA. Email: [email protected] lignin oligomers. Funding information Methods: Synthesized lignin oligomers were analyzed using the developed MALDI National Science Foundation, Grant/Award method. Two matrix systems, DHAP and α‐cyano‐4‐hydroxycinnamic acid (CHCA), Number: OIA 1632854 and three cations (lithium, sodium, silver) were evaluated using a Bruker UltraFlextreme time‐of‐flight mass spectrometer. Instrumental parameters, cation concentration, matrix, sample concentrations, and sample spotting protocols were optimized for improved results. Results: The DHAP/Li+ combination was effective for dimer analysis as lithium adducts. Spectra from DHP and ferric chloride oligomers showed improved signal intensities up to decamers (m/z 1823 for the FeCl3 system) and provided insights into differences in the oligomerization mechanism. Spectra from a mixed DHP oligomer system containing H, G, and S units showed contributions from all monolignols within an oligomer level (e.g.
    [Show full text]
  • Synthesis and Biosynthesis of Polyketide Natural Products
    Syracuse University SURFACE Chemistry - Dissertations College of Arts and Sciences 12-2011 Synthesis and Biosynthesis of Polyketide Natural Products Atahualpa Pinto Syracuse University Follow this and additional works at: https://surface.syr.edu/che_etd Part of the Chemistry Commons Recommended Citation Pinto, Atahualpa, "Synthesis and Biosynthesis of Polyketide Natural Products" (2011). Chemistry - Dissertations. 181. https://surface.syr.edu/che_etd/181 This Dissertation is brought to you for free and open access by the College of Arts and Sciences at SURFACE. It has been accepted for inclusion in Chemistry - Dissertations by an authorized administrator of SURFACE. For more information, please contact [email protected]. Abstract Traditionally separate disciplines of a large and broad chemical spectrum, synthetic organic chemistry and biochemistry have found in the last two decades a fertile common ground in the area pertaining to the biosynthesis of natural products. Both disciplines remain indispensable in providing unique solutions on numerous questions populating the field. Our contributions to this interdisciplinary pursuit have been confined to the biosynthesis of polyketides, a therapeutically and structurally diverse class of natural products, where we employed both synthetic chemistry and biochemical techniques to validate complex metabolic processes. One such example pertained to the uncertainty surrounding the regiochemistry of dehydration and cyclization in the biosynthetic pathway of the marine polyketide spiculoic acid A. The molecule's key intramolecular cyclization was proposed to occur through a linear chain containing an abnormally dehydrated polyene system. We synthesized a putative advanced polyketide intermediate and tested its viability to undergo a mild chemical transformation to spiculoic acid A. In addition, we applied a synthetic and biochemical approach to elucidate the biosynthetic details of thioesterase-catalyzed macrocyclizations in polyketide natural products.
    [Show full text]
  • And Even-Length, Medium-Chain Fatty Acids in Plants (Amino Adds/Elongtin) ANTOANETA B
    Proc. Nadl. Acad. Sci. USA Vol. 91, pp. 11437-11441, November 1994 Biochemistry A pathway for the biosynthesis of straight and branched, odd- and even-length, medium-chain fatty acids in plants (amino adds/elongtin) ANTOANETA B. KROUMOVA, ZHIYI XIE, AND GEORGE J. WAGNER* Plant Physiology/Biochemistry/Molecular Biology Program, Agronomy Department, University of Kentucky, Lexington, KY 40546-0091 Communicated by Martin Gibbs, July 25, 1994 ABSTRACT Pathways and enzymes offatty acid synthase- and even-length scFAs are synthesized via modified mediated, long-even-chain (generally C16-C20) fatty add syn- branched-chain amino acid (bcAA) metabolism in tobacco thesis are well studied, and general metabolism involved in trichome glands (6, 7). It is possible that at least branched and short-chain (Cs-C7) fatty acid biosynthesis is also understood. odd-length mcFAs are formed in this tissue similarly. Alter- In contrast, mechanism of medinm-chain (C#-C14) fatty acid natively, primers derived from bcAA metabolism may be synthesis are unclear. Recent work suggests involvement of elongated by fatty acid synthase (FAS), as suggested for chain-elongation-terminating thloesterases in medium-chain tomato trichomes (8) and tobacco epidermis (9). fatty acid formation in oilseeds and animals. We have shown The classical pathway for bcAA (Val, Leu, Ileu) biosyn- that iso- and anteiso-branched and straigbt, odd- and even- thesis in microorganisms (and largely by inference in plants, length, short-chain fatty adds esterifled in plant-trichome- ref. 10) is shown in the shaded areas of Fig. 1. Key activities gland-produced sucrose esters are synthesized by using carbon involved in branched-chain formation (reactions 1, 1A, and 2) skeletons provided by modified branched-chain amino acid are those catalyzing leucine biosynthesis in all organisms and metabolism/catablis.
    [Show full text]
  • Spontaneous Generation & Origin of Life Concepts from Antiquity to The
    SIMB News News magazine of the Society for Industrial Microbiology and Biotechnology April/May/June 2019 V.69 N.2 • www.simbhq.org Spontaneous Generation & Origin of Life Concepts from Antiquity to the Present :ŽƵƌŶĂůŽĨ/ŶĚƵƐƚƌŝĂůDŝĐƌŽďŝŽůŽŐLJΘŝŽƚĞĐŚŶŽůŽŐLJ Impact Factor 3.103 The Journal of Industrial Microbiology and Biotechnology is an international journal which publishes papers in metabolic engineering & synthetic biology; biocatalysis; fermentation & cell culture; natural products discovery & biosynthesis; bioenergy/biofuels/biochemicals; environmental microbiology; biotechnology methods; applied genomics & systems biotechnology; and food biotechnology & probiotics Editor-in-Chief Ramon Gonzalez, University of South Florida, Tampa FL, USA Editors Special Issue ^LJŶƚŚĞƚŝĐŝŽůŽŐLJ; July 2018 S. Bagley, Michigan Tech, Houghton, MI, USA R. H. Baltz, CognoGen Biotech. Consult., Sarasota, FL, USA Impact Factor 3.500 T. W. Jeffries, University of Wisconsin, Madison, WI, USA 3.000 T. D. Leathers, USDA ARS, Peoria, IL, USA 2.500 M. J. López López, University of Almeria, Almeria, Spain C. D. Maranas, Pennsylvania State Univ., Univ. Park, PA, USA 2.000 2.505 2.439 2.745 2.810 3.103 S. Park, UNIST, Ulsan, Korea 1.500 J. L. Revuelta, University of Salamanca, Salamanca, Spain 1.000 B. Shen, Scripps Research Institute, Jupiter, FL, USA 500 D. K. Solaiman, USDA ARS, Wyndmoor, PA, USA Y. Tang, University of California, Los Angeles, CA, USA E. J. Vandamme, Ghent University, Ghent, Belgium H. Zhao, University of Illinois, Urbana, IL, USA 10 Most Cited Articles Published in 2016 (Data from Web of Science: October 15, 2018) Senior Author(s) Title Citations L. Katz, R. Baltz Natural product discovery: past, present, and future 103 Genetic manipulation of secondary metabolite biosynthesis for improved production in Streptomyces and R.
    [Show full text]
  • Methyltransferases of Gentamicin Biosynthesis
    Methyltransferases of gentamicin biosynthesis Sicong Lia,1, Junhong Guoa,1, Anna Revab, Fanglu Huangb, Binbin Xionga, Yuanzhen Liua, Zixin Denga,c, Peter F. Leadlayb,2, and Yuhui Suna,2 aKey Laboratory of Combinatorial Biosynthesis and Drug Discovery, Ministry of Education, School of Pharmaceutical Sciences, Wuhan University, Wuhan 430071, People’s Republic of China; bDepartment of Biochemistry, University of Cambridge, Cambridge CB2 1GA, United Kingdom; and cState Key Laboratory of Microbial Metabolism, School of Life Sciences & Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, People’s Republic of China Edited by Caroline S. Harwood, University of Washington, Seattle, WA, and approved December 26, 2017 (received for review June 30, 2017) Gentamicin C complex from Micromonospora echinospora re- G418 (5) to gentamicin components C2a, C2, and C1. The mains a globally important antibiotic, and there is revived in- full mechanistic details of the subsequent transamination and terest in the semisynthesis of analogs that might show improved dehydroxylation steps remain to be clarified, although the de- therapeutic properties. The complex consists of five compo- hydrogenase GenQ (20), phosphotransferase GenP, and the nents differing in their methylation pattern at one or more sites pyridoxal-dependent enzymes GenB1, GenB2, GenB3, and in the molecule. We show here, using specific gene deletion and GenB4 have all been implicated in this enigmatic process (20, 25, chemical complementation, that the gentamicin pathway up to 26). Finally, the terminal step in both branches of the pathway the branch point is defined by the selectivity of the methyl- involves the (partial) conversion of C1a into C2b and of C2 transferases GenN, GenD1, and GenK.
    [Show full text]
  • Plant Sulphur Metabolism Is Stimulated by Photorespiration
    ARTICLE https://doi.org/10.1038/s42003-019-0616-y OPEN Plant sulphur metabolism is stimulated by photorespiration Cyril Abadie1,2 & Guillaume Tcherkez 1* 1234567890():,; Intense efforts have been devoted to describe the biochemical pathway of plant sulphur (S) assimilation from sulphate. However, essential information on metabolic regulation of S assimilation is still lacking, such as possible interactions between S assimilation, photo- synthesis and photorespiration. In particular, does S assimilation scale with photosynthesis thus ensuring sufficient S provision for amino acids synthesis? This lack of knowledge is problematic because optimization of photosynthesis is a common target of crop breeding and furthermore, photosynthesis is stimulated by the inexorable increase in atmospheric CO2. Here, we used high-resolution 33S and 13C tracing technology with NMR and LC-MS to access direct measurement of metabolic fluxes in S assimilation, when photosynthesis and photorespiration are varied via the gaseous composition of the atmosphere (CO2,O2). We show that S assimilation is stimulated by photorespiratory metabolism and therefore, large photosynthetic fluxes appear to be detrimental to plant cell sulphur nutrition. 1 Research School of Biology, Australian National University, Canberra, ACT 2601, Australia. 2Present address: IRHS (Institut de Recherche en Horticulture et Semences), UMR 1345, INRA, Agrocampus-Ouest, Université d’Angers, SFR 4207 QuaSaV, 49071 Angers, Beaucouzé, France. *email: guillaume. [email protected] COMMUNICATIONS BIOLOGY
    [Show full text]
  • Development of a Four-Step Semi-Biosynthesis of the Anticancer Drug Paclitaxel and Its Analogues
    DEVELOPMENT OF A FOUR-STEP SEMI-BIOSYNTHESIS OF THE ANTICANCER DRUG PACLITAXEL AND ITS ANALOGUES By Chelsea Thornburg A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of Biochemistry and Molecular Biology ‒ Doctor of Philosophy 2015 ABSTRACT DEVELOPMENT OF A FOUR-STEP SEMI-BIOSYNTHESIS OF THE ANTICANCER DRUG PACLITAXEL AND ITS ANALOGUES By Chelsea Thornburg Paclitaxel (Taxol®) is a widely used chemotherapeutic drug with additional medical applications in drug-eluting stents as an anti-restenosis treatment. Paclitaxel is a structurally complex natural product with an excellent scaffold for designing analogs with pharmacological properties. To date, clinically approved analogs include docetaxel and cabazitaxel for the treatment of additional cancers. Currently, plant cell fermentation methods produce paclitaxel and large quantities of the precursors 10-deacetylbaccatin III (10-DAB) and baccatin III. The complexity of the semi-characterized ~19-step paclitaxel biosynthetic pathway limits bioengineering attempts. However, the availability of 10-DAB and baccatin III suggests a semi-biosynthetic pathway to paclitaxel starting with these precursors is feasible. We have designed a short, simple biosynthetic pathway, capable of making paclitaxel, analogs, and/or valuable precursors for the semi-synthesis of additional analogs of biological interest. The paclitaxel biosynthesis enzyme baccatin III: 3-amino-13-O-phenylpropanoyl CoA transferase (BAPT) and the bacterial (2R,3S)-phenylisoserinyl CoA ligase (PheAT) produce N-debenzoylpaclitaxel, N-debenzoyldocetaxel, or precursor analogs. The addition of the paclitaxel biosynthetic N-debenzoyltaxol-N-benzoyltransferase (NDTNBT) and the bacterial benzoate CoA ligase (BadA) produce paclitaxel or other N-acylated analogs. In this dissertation, BAPT and BadA are kinetically characterized.
    [Show full text]
  • Fusing Catalase to an Alkane-Producing Enzyme
    Fusing catalase to an alkane-producing enzyme maintains enzymatic activity by converting the inhibitory byproduct H2O2 to the cosubstrate O2 Carl Andre1, Sung Won Kim, Xiao-Hong Yu, and John Shanklin2 Biosciences Department, Brookhaven National Laboratory, Upton, NY 11973 Edited by Rodney B. Croteau, Washington State University, Pullman, WA, and approved December 31, 2012 (received for review October 29, 2012) Biologically produced alkanes represent potential renewable alter- enzyme was determined as part of a structural genomics effort natives to petroleum-derived chemicals. A cyanobacterial pathway (Protein Data Bank 2OC5, Joint Center for Structural Genom- consisting of acyl–Acyl Carrier Protein reductase and an aldehyde- ics). ADO converts aldehydes to n-1 alkanes with the aldehyde C1 deformylating oxygenase (ADO) converts acyl–Acyl Carrier Pro- released as formic acid (8, 9). Electrons required for the reaction teins into corresponding n-1 alkanes via aldehyde intermediates can be provided by NADPH via ferredoxin-NADP reductase in an oxygen-dependent manner (Km for O2,84± 9 μM). In vitro, (FNR), and ferredoxin (Fd) (7), or via the chemical mediator ADO turned over only three times, but addition of more ADO to phenazine methosulfate (PMS) (10). A proposed reaction scheme exhausted assays resulted in additional product formation. While for ADO (adapted from ref. 9) is depicted below where R evaluating the peroxide shunt to drive ADO catalysis, we discov- represents Acyl: ered that ADO is inhibited by hydrogen peroxide (H2O2) with an apparent Ki of 16 ± 6 μM and that H2O2 inhibition is of mixed-type with respect to O2. Supplementing exhausted assays with catalase (CAT) restored ADO activity, demonstrating that inhibition was reversible and dependent on H2O2, which originated from poor coupling of reductant consumption with alkane formation.
    [Show full text]
  • Directed Biosynthesis of Fluorinated Polyketides
    bioRxiv preprint doi: https://doi.org/10.1101/2021.07.30.454469; this version posted July 30, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license. Title: Directed biosynthesis of fluorinated polyketides Authors: Alexander Rittner‡1, Mirko Joppe‡1, Jennifer J. Schmidt2, Lara Maria Mayer1, Elia Heid1, David H. Sherman2 and Martin Grininger1* Affiliations: 1 Institute of Organic Chemistry and Chemical Biology, Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt; Max-von-Laue-Str. 15, Frankfurt am Main, D-60438, Germany 2 Life Sciences Institute, University of Michigan; Ann Arbor, Michigan 48109, USA *Corresponding author. Email: [email protected] ‡These authors contributed equally to this work Abstract: Modification of polyketides with fluorine offers a promising approach to develop new pharmaceuticals. While synthetic chemical methods for site-specific incorporation of fluorine in complex molecules have improved in recent years, approaches for the direct biosynthetic fluorination of natural compounds are still rare. Herein, we present a broadly applicable approach for site-specific, biocatalytic derivatization of polyketides with fluorine. Specifically, we exchanged the native acyltransferase domain (AT) of a polyketide synthase (PKS), which acts as the gatekeeper for selection of extender units, with an evolutionarily related but substrate tolerant domain from metazoan type I fatty acid synthase (FAS). The resulting PKS/FAS hybrid can utilize fluoromalonyl coenzyme A and fluoromethylmalonyl coenzyme A for polyketide chain extension, introducing fluorine or fluoro-methyl disubstitutions in polyketide scaffolds.
    [Show full text]